The sludge of a whole other…
The sludge of a whole other is far more than likely from an oil and filter change never being done in 100, 000 miles if I'm betting on any possible scenario. Adding a quart or two of oil to the crankcase who knows how often with as much as that had to be leaking is the one thing that kept that motor from locking up I should add in my opinion, along with the owner thinking adding a quart or two to the crank case every 1,000 miles at best being their idea of an "oil change"